diff --git a/frontend/src/lib/components/PersonMentionEditor.svelte b/frontend/src/lib/components/PersonMentionEditor.svelte
index 81a9f8fd..3a9188c1 100644
--- a/frontend/src/lib/components/PersonMentionEditor.svelte
+++ b/frontend/src/lib/components/PersonMentionEditor.svelte
@@ -123,6 +123,20 @@ onMount(() => {
 				},
 				suggestion: {
 					char: '@',
+					// ─────────────────────────────────────────────────────────────
+					// EXCEPTION to frontend/CLAUDE.md "no client-side API fetch":
+					// Tiptap's suggestion plugin lives entirely on the client and
+					// fires on every keystroke after `@`. Routing each query through
+					// a SvelteKit form action would round-trip through SSR for a
+					// dropdown that needs to feel instantaneous, and a +server.ts
+					// endpoint would only proxy the same call. Auth flows through
+					// the Vite proxy in dev and Caddy in prod (cookie-based), so the
+					// network surface is identical to a server-driven call.
+					// Markus #5616: an ADR will formalise this. Open follow-up:
+					// "ADR: client-side fetch exception for editor suggestion plugins."
+					// Nora #5618 #3 — separate issue tracks the GET /api/persons
+					// response-shape audit (PersonSummaryDTO leaks `notes`).
+					// ─────────────────────────────────────────────────────────────
 					items: async ({ query }: { query: string }) => {
 						if (!query) return [];
 						try {